With the increase of the power of a router, an entire enterprise network equipment, and a board, some high-power subrack-shaped equipment requires that a direct current/direct current (DC/DC) voltage regulator module in a system supports flexible configuration, so as to meet customers' requirements for investment and power distribution in an equipment room. To improve the conversion efficiency of a DC/DC voltage regulator module, a single-inductor buck-boost (BUCK-BOOST) topology is used, which is a topological structure supporting a DC/DC voltage regulator module in achieving high efficiency.
FIG. 1 is a circuit diagram of a single-inductor buck-boost topology in the prior art. As illustrated in FIG. 1, a metal-oxide-semiconductor field-effect transistor (MOSFET) T1, a MOSFET T3, an inductor L1 form a buck conversion circuit, that is, a BUCK circuit, and a MOSFET T2, a MOSFET T4, the inductor L1 form a boost conversion circuit, that is, a BOOST circuit. The circuit of the topology needs to, based on an input signal, perform a switchover among three topology states: buck, pass, and boost.
Currently, a method for controlling a switchover among three topology states is to check the state of an input signal by using three comparators. The state of an input signal is transmitted to a complex programmable logic device (CPLD) by using an optocoupler. Then, the CPLD determines the state of the BUCK-BOOST topology based on the state of the input signal. Finally, a pulse width modulation (PWM) controller controls a switchover among three topology states based on the state of the BUCK-BOOST topology. For example, when an input signal is in the range from 36 volts (V) to 48V, the topology enters the BOOST state; when the input signal is in the range from 46V to 54V, the topology enters the PASS state; and when the input signal is in the range from 52V to 72V, the topology enters the BUCK state. When a topology state switchover is being performed, the state of the PWM controller also changes suddenly. To prevent the state of a PWM controller from changing suddenly, a soft start needs to be implemented during a switchover among three topology states: buck, boost, and pass. The foregoing control method is capable of achieving a switchover among three topology states: BUCK, PASS, and BOOST.
However, specific implementation of the control method is very complicated, and the implementation circuit includes a power nonconventional device like CPLD. In addition, because the adjustment output signal in the BUCK state is different from the adjustment output signal in the BOOST state due to the issue related to the maximum duty cycle of a PWM controller, different modules cannot be in the BUCK state and the BOOST state simultaneously, directly resulting in that different modules cannot work in a scenario in which input signals dramatically differ from each other. The prior art cannot meet the demand that a system requires a plurality of DC/DC voltage regulator modules to work in parallel and achieve current equalization.